Light source unit utilizing laser for light source and projector

ABSTRACT

A light source unit includes a light emitting plate which has a plurality of segment areas and in which a luminescent material layer which emits light having a predetermined wavelength band by receiving excitation light and a transmissive portion which transmits light are formed on at least the plurality of segment areas, a primary light source for emitting excitation light on to the luminescent material, a secondary light source for emitting light having a wavelength band which differs from those of luminescent light emitted from the luminescent material layer and excitation light emitted from the primary light source, a light guiding optical system for guiding light emitted from the light emitting plate and light emitted from the secondary light source to the same optical path, and a light source control means for controlling the emission of light from the primary light source and the secondary light source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional of U.S. application Ser. No. 12/825,579, filed Jun.29, 2010 now U.S. Pat. No. 8,308,306, which is based upon and claims thebenefit of priority under 35 USC 119 of Japanese Patent Application No.2009-155452, filed Jun. 30, 2009, the entire contents of both of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light source unit which utilizeslaser for a light source and a projector which includes the light sourceunit.

2. Description of the Related Art

In these days, data projectors are used in many cases as imageprojection apparatuses which project images including video images shownon screens of personal computers on to a screen, and the data projectorsfurther read out image data or dynamic image data stored in memory cardsfor projection on to the screen. These projectors are such that lightemitted from a light source is concentrated on a micromirror devicecalled a DMD (Digital Micromirror Device) or a liquid crystal plate fordisplay of a color image on the screen.

In projectors of the type described above, conventionally, projectorsusing a high-intensity discharge lamp as a light source have been themainstream of projectors. In recent years, however, there have been mademany developments and proposals on light source units which utilize as alight source a light emitting diode or a laser diode, or devicesutilizing organic EL technology or luminescence technology usingluminescent materials. For example, a light source unit described inJapanese Unexamined Patent Publication No. 2004-341105(JP-A-2004-341105) includes a luminescent wheel which is made up of adisc-shaped transparent base material on which a luminescent materiallayer is disposed and a solid-state light source which emits ultravioletlight, and the luminescent wheel is described as converting ultravioletlight received into visible light. In the light source unit described inJP-A-2004-341105, ultraviolet light is shone on to the luminescentmaterial layer formed on the luminescent wheel as excitation light, sothat luminescent light having red, green and blue wavelength bands canbe emitted.

However, since the light emitting efficiency of the red luminescentmaterial is remarkably lower than those of the other luminescentmaterials, there has been caused a problem that the luminance of redbecomes insufficient.

SUMMARY OF THE INVENTION

The invention has been made in view of the problem inherent in therelated art and an object thereof is to provide a light source unitincluding a luminescent wheel having a luminescent material of a kindhaving a good light emitting efficiency, a light source for exciting theluminescent material, and a single-color light source for emitting lighthaving a corresponding wavelength band to a luminescent material of akind having a relatively low light emitting efficiency to therebyincrease a luminance of a screen, and a projector including this lightsource.

According to a preferred aspect of the invention, there is provided alight source unit including:

-   -   a light emitting plate which has a plurality of segment areas        and in which a luminescent material layer which emits light        having a predetermined wavelength band by receiving excitation        light and a transmissive portion which transmits light are        formed on at least the plurality of segment areas;    -   a primary light source for emitting excitation light on to the        luminescent material;    -   a secondary light source for emitting light having a wavelength        band which differs from those of luminescent light emitted from        the luminescent material layer and excitation light emitted from        the primary light source;    -   a light guiding optical system for guiding light emitted from        the light emitting plate and light emitted from the secondary        light source to the same optical path; and    -   a light source control means for controlling the emission of        light from the primary light source and the secondary light        source.

Namely, the light source unit is provided which can emit highly luminouslight of a plurality of colors, and the light source unit can emit suchlight while time-sharing the plurality of colors. Then, by making thelight source unit into a light source unit which emits at least light ofthe three primary colors, the resulting light source unit can besuitable for optical equipment such as a projector.

In addition, according to another preferred aspect of the invention,there is provided a projector having the light source unit describedabove. By being equipped with the light source unit, although it issmall in size, the projector can be made into a projector which canproject an image which is bright and superior in tone.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and further objects, characteristics and advantages of theinvention will be more obvious from accompanying drawings and thefollowing detailed description of the invention. In the drawings,

FIG. 1 is a perspective view showing an external appearance of aprojector which includes a light source unit according to an embodimentof the invention,

FIG. 2 is a functional circuit block diagram of the projector whichincludes the light source unit according to the embodiment of theinvention,

FIG. 3 is an exemplary plan view showing an internal construction of theprojector includes the light source unit according to the embodiment ofthe invention,

FIG. 4 shows an exemplary front view of a luminescent wheel according tothe embodiment of the invention and an exemplary plan view of theluminescent wheel which is partially sectioned,

FIG. 5 is an exemplary plan view of the light source unit according tothe embodiment of the invention,

FIG. 6 shows exemplary front views of the luminescent wheel which showprimary light source turn-off ranges according to the embodiment of theinvention,

FIG. 7 shows time charts depicting timings at which a primary lightsource and a secondary light source are turned on and off by a lightsource control means according to the embodiment of the invention,

FIG. 8 shows exemplary front views of another form of a luminescentwheel in the light source unit according to the embodiment of theinvention,

FIG. 9 is an exemplary plan view of a light source unit according to amodified example of the invention, and

FIG. 10 is an exemplary front view of a luminescent wheel of the lightsource unit according to the modified example of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, a best mode for carrying out the invention will bedescribed by use of the accompanying drawings. However, in the followingembodiment, although various preferred technical limitations will bedescribed as being made for carrying out the invention, the scope of theinvention is not limited at all to the following embodiment andillustrated examples.

Firstly, the configurations of a projector of the invention and a lightsource unit which is incorporated in the projector will be summarized.

A projector 10 includes a light source unit 63, a display device 51, acooling fan, a light source side optical system 62 for guiding lightfrom the light source unit 63 to the display device 51, a projectionside optical system 90 for projecting an image emitted from the displaydevice 51 on to a screen, a projector control means for controlling thelight source unit 63 and the display device 51, and a light sourcecontrol circuit 41 which is a light source control means for controllingtimings at which a primary light source 72 and a secondary light source82 of the light source unit 63 are turned on.

Then, in the light source unit 63, a dichroic mirror 151 is disposed ina position where an optical axis of the primary light source unit 72 andan optical axis of the secondary light source unit 82 intersect eachother. This dichroic mirror 151 transmits light from the primary lightsource 72 which has passed through a luminescent wheel 71 andluminescent light emitted from the luminescent wheel 71 and reflectslight from the secondary light source 82. This dichroic mirror 151prevents light from the secondary light source 82 from entering theluminescent wheel 71.

This light source unit 63 includes the luminescent wheel 71 which hastwo semicircular segment areas lying adjacent to each other on atransparent base material whose rotation can be controlled and in whicha luminescent material layer 131 which emits light having a greenwavelength band by receiving excitation light is formed in a first area1 which is one of the segment areas and a transmissive portion whichtransmits light is formed in a second area 2 which is the other segmentarea, the primary light source 72 for emitting excitation light in avisible light wavelength band on to the luminescent material, thesecondary light source 82 for emitting light having a wavelength bandwhich differs from those of luminescent light emitted from theluminescent material layer 131 and excitation light emitted from theprimary light source 72, and a light guiding optical system for guidinglight emitted from the luminescent wheel 71 and light emitted from thesecondary light source 82 to the same optical path.

In addition, the transparent base material is formed of a glass basematerial or a transparent resin base material. A dichroic layer 132 isformed on a surface of the first area 1 of the transparent base materialon which the luminescent material layer 131 is to be disposed throughcoating. This dichroic layer 132 transmits excitation light but reflectslight having other wavelength bands.

Additionally, a diffuse layer 141 is formed on the second area 2 of thetransparent base material, and this diffuse layer 141 diffuses lightwhich is transmitted therethrough. Further, a nonreflective coated layeris formed through coating over an overall surface of a side of thetransparent base material which is opposite to the side on which theluminescent layer 131 is disposed.

In addition, the primary light source 72 is a laser emitter which emitslight which has a blue wavelength band and whose wavelength is shorterthan that of light having a green wavelength band and emitted from thegreen luminescent material layer 131. The secondary light source 82 is alight emitting diode which emits light of a red wavelength band.

Additionally, the light source control means is configured so as to turnoff the primary light source 72 and turn on the secondary light source82 so as to prevent the emission of light having a wavelength band whichis a combination of wavelength bands of two colors from the luminescentwheel 71, which would otherwise occur by light from the primary lightsource 72 entering so that an illumination area 7 stretches over thefirst area 1 and the second area 2 at a boundary between the two segmentareas.

Hereinafter, an embodiment of the invention will be described byreference to the accompanying drawings.

FIG. 1 is a perspective view showing an external appearance of aprojector 10. In this embodiment, left and right denote, respectively,left and right directions with respect to a projecting direction of theprojector 10, and front and rear denote, respectively, front and reardirections with respect to a traveling direction of a light beam emittedfrom the projector 10. As is shown in FIG. 1, the projector 10 has asubstantially rectangular parallelepiped shape and has a lens cover 19which covers a projection port which lies to a side of a front panel 12which is referred to as a front side panel of a main body case, as wellas a plurality of inside air outlet holes 17 in the front panel 12.Further, although not shown, the projector 10 includes an Ir receptionpart for receiving a control signal from a remote controller.

In addition, a keys/indicators part 37 is provided on an upper sidepanel 11 which makes up the main body case. Disposed on thiskeys/indicators part 37 are keys and indicators which include a powersupply switch key, a power indicator which informs whether the powersupply is on or off, a projection switch key which switches on or offprojection, an overheat indicator which informs of an overheat conditionwhen the light source unit, the display device or the control circuitoverheats and the like.

Further, provided on a back side or a back side panel of the main bodycase are an input/output connectors part where USB terminals, an imagesignal input D-SUB terminal, an S terminal, an RCA terminal and the likeare provided and various types of terminals 20 including a power supplyadaptor plug and the like. A plurality of outside air inlet holes 18 areformed in proximity to lower portions of a right-hand side panel 14which constitutes a side panel, not shown, of the main body case and aleft-hand side panel 15 which is a side panel shown in FIG. 1.

Next, a projector control means for the projector 10 will be describedby use of a block diagram in FIG. 2.

The projector control means is made up of a control unit 38, aninput/output interface 22, an image transform part 23, a display encoder24, a display drive part 26 and the like. Image signals of variousstandards that are inputted from the input/output connector part 21 aresent via the input/output interface 22 and a system bus (SB) to theimage transform part 23 where the image signals are transformed so as tobe unified into an image signal of a predetermined format which issuitable for display. Thereafter, the image signals so transformed arethen outputted to the display encoder 24.

The control unit 38 governs the control of respective operations ofcircuitries within the projector 10 and is made up of a CPU, a ROM whichstores in a fixed fashion operation programs of various types ofsettings and a RAM which is used as a work memory.

In addition, the display encoder 24 deploys the image signals inputtedthereinto on a video RAM 25 for storage therein and generates a videosignal from the contents stored in the video RAM 25, outputting thevideo signal so generated to the display drive part 26.

The display drive part 26 drives a display device 51 which is a spatialoptical modulator (SOM) at an appropriate frame rate in accordance withthe image signal outputted from the display encoder 24. Namely, a lightbeam emitted from the light source unit 63 is caused to be incident onthe display device 51 via a light source side optical system to therebyform an optical image by reflected light reflected at the display device51. Then, the image so formed is projected on to a screen, not shown,for display via a projection system lens group which is referred to as aprojection side optical system. A movable lens group 97 of theprojection side optical system is driven by a lens motor 45 for zoomingor focusing.

In addition, an image compression/expansion part 31 performs a recordingoperation in which a luminance signal and a color-difference signal ofthe image signal are data compressed through processings such as ADCTand Huffman coding so as to write them sequentially on a memory card 32which is referred to as a detachable recording medium. Further, theimage compression/expansion part 31 performs an operation in which whenin a reproducing mode, the image compression/expansion part 31 reads outimage data recorded on the memory card 32 and expands individual imagedata which make up a series of dynamic images frame by frame. Then, theimage data is outputted to the display encoder 24 via the imagetransform part 23 so as to enable the display of dynamic images on thebasis of the image data stored on the memory card 32.

Operation signals generated at the keys/indicators part 37 which is madeup of the main keys and indicators provided on the upper side panel 11of the main body case are sent out directly to the control unit 38,while key operation signals generated by operating keys on the remotecontroller are received by the Ir reception part 35, and a code signaldemodulated at an Ir processing part 36 is outputted to the control unit38.

In addition, a voice processing part 47 is connected to the control unit38 via the system bus (SB). This voice processing part 47 includes asound source circuit such as a PCM sound source. When in a projectionmode and a reproducing mode, the voice processing part 47 converts voicedata into analog signals and drives a speaker 48 to output loudly soundor voice based on the voice data.

Additionally, the control unit 38 controls a light source controlcircuit 41 which is the light source control means. This light sourcecontrol circuit 41 controls the emission of light from the primary lightsource and the secondary light source of the light source unit 63 inaccordance with an image signal. Further, the control unit 38 causes acooling fan drive control circuit 43 to detect temperatures through aplurality of sensors which are provided at the light source unit 63 andthe like so as to control the rotational speed of the cooling fan basedon the results of the temperature detection.

In addition, the control unit 38 also causes the cooling fan drivecontrol circuit 43 to make the cooling fan continue to rotate even afterthe power supply of the projector main body is switched off by use of atimer or the like or to make the power supply to the projector main bodybe cut off depending upon the results of the temperature detection bythe temperature sensors.

Next, an internal construction of the projector 10 will be described.

FIG. 3 is an exemplary plan view showing an internal construction of theprojector 10.

As is shown in FIG. 3, in the projector 10, a light source controlcircuit board 102 is disposed in proximity to the right-hand side panel14 and a power supply circuit block 101 and the like are mounted on thislight source control circuit board 12. A sirocco fan-type blower 110 isdisposed substantially at a center in the projector 10. In addition, acontrol circuit board 103 is disposed in proximity to the blower 110,and the light source 63 is disposed in proximity to the front panel 12,an optical system unit 70 being disposed in proximity to the left-handside panel 15. Additionally, an interior of a housing of the projector10 is divided airtightly into an inlet side space compartment 121 whichlies on the back panel 13 side and an outlet side space compartment 122which lies on the front panel 12 side by a portioning bulkhead 120. Theblower 110 is disposed so that its outside air inlet port 111 ispositioned in the inlet side space compartment 121 and its outside airoutlet port 113 is positioned on a boundary between the outlet sidespace compartment 122 and the inlet side space compartment 121.

The optical system unit 70 has a substantially U-shape and is made up ofthree blocks such as an illumination side block 78 which is positionedin proximity to the light source unit 63, an image generation block 79which is positioned on the back panel 13 side, and a projection sideblock 80 which is positioned between the illumination side block 78 andthe left-hand side panel 15.

The illumination side block 78 includes part of a light source sideoptical system 62 for guiding light emitted from the light source unit63 to the display device 51 which is included in the image generationblock 79. A light mixing unit 75 for making a light beam emitted fromthe light source 63 into a light beam whose intensity is uniformlydistributed and a light guiding lens for concentrating light that haspassed through the light mixing unit 75 are included in the light sourceside optical system 62 that is included in the illumination side block78.

The image generating block 79 has, as the light source side opticalsystem 62, an optical axis varying mirror 74 for varying a direction ofan optical axis of the light beam that has emerged from the light mixingunit 75, a plurality of light guiding lenses for concentrating lightreflected by the optical axis varying mirror 74 on the display device 51and a shining mirror 84 for shining the light beam that has passedthrough the light guiding lenses on to the display device 51 at apredetermined angle. Further, the image generating block 79 includes aDMD which is configured as the display device 51, and a display deviceheatsink or cooling device 53 for cooling the display device 51 isdisposed on a back panel 13 side of the display device 51 to therebyprevent the display device 51 from being heated to a high temperature.

The projection side block 80 has a lens group of a projection sideoptical system 90 which projects light on to the screen, which light isreflected by the display device 51 to form an image. The projection sideoptical system 90 constitutes a variable focus lens made up of a fixedlens group 93 which is incorporated in a fixed lens barrel and a movablelens group 97 which is incorporated in a movable lens barrel and havinga zooming function. This variable focus lens enables zooming andfocusing operations by moving the movable lens group 97 by a lens motor.

In addition, in the interior construction of the projector 10, membersthat are heated to lower temperatures than the light source unit 63 aredisposed within the inlet side space compartment 121. Specifically,disposed in the inlet side space compartment 121 are the light sourcecontrol circuit board 102, the blower 110, the control circuit board103, the image generation block 79 of the optical system unit 70, theprojection side block 80 of the optical system unit 70 and the lightguiding lens in the illumination side block 78 of the optical systemunit 70.

On the other hand, disposed in the outlet side space compartment 122 arethe light source unit 63 which is heated to relatively hightemperatures, the light mixing unit 75 included in the illumination sideblock 78 of the optical system unit 70, and an outlet air temperaturereducing unit 114.

Then, the light source unit 63 includes a luminescent wheel 71 foremitting light having wavelength bands of green and blue which are theprimary colors of light by entering of light corresponding thereto, awheel motor 73 which is a drive unit for driving to rotate theluminescent wheel 71, a primary light source 72 for emitting light ofblue wavelength band on to the luminescent wheel 71, and a secondarylight source 82 for emitting light of red wavelength band.

Then, the primary light source 72 is disposed so that an optical axis ofthe primary light source 72 is substantially at right angles to anoptical axis of the light mixing unit 75. In addition, the secondarylight source 82 is disposed so that an optical axis of the secondarylight source 82 becomes substantially parallel to the optical axis ofthe light mixing unit 75. The luminescent wheel 71 is disposed in aposition where the optical axis of the primary light source 72intersects a wheel surface of the luminescent wheel 71 at right angles.In other words, a rotating axis of the wheel motor 73 for rotating theluminescent wheel 71 is parallel to the optical axis of the primarylight source 72.

This primary light source 72 is designed to emit light on to aluminescent material layer 131 which is disposed in proximity to anouter circumferential portion of the luminescent wheel 71 and thediffuse layer 141. The primary light source 72 is configured as a laseremitter which emits light having a blue wavelength band which is visiblelight whose wavelength is shorter than that of light having a greenwavelength band that is emitted from the luminescent material layer 131.In addition, the secondary light source 82 is configured as a red lightemitting diode which emits light having a red wavelength band.

As is shown in FIG. 4, the luminescent wheel 71 is a thin circulartransparent base material which includes the luminescent material layer131. A circular opening is formed in a central portion of thetransparent base material, and the circular opening so formedcorresponds to a shape of a cylindrical rotating shaft which constitutesa connecting portion to the wheel motor 73. The rotating shaft issecurely inserted into the circular opening and a motor hub is bonded tothe transparent base material in a position lying in proximity to thecentral portion thereof, whereby the luminescent wheel 71 is stronglyand rigidly connected to the rotating shaft of the wheel motor 73.

Consequently, this luminescent wheel 71 is able to rotate in acircumferential direction integrally by the wheel motor 73 as a drivingunit which is controlled to be driven at a rotational speed of about 120revolutions per second by the control unit 38 of the projector controlmeans. Namely, the luminescent wheel 71 is designed to be controlledrotationally.

The transparent base material has two semicircular segment areas whichlie adjacent to each other and is formed of a glass base material or atransparent resin base material. In this transparent base material, theluminescent material layer 131 is formed on a first area 1 which is oneof the segment areas, while a transmissive portion is formed on a secondarea 2 which is the other segment area, and this transmissive portion isdesigned to transmit light from the primary light source 72.

Then, a belt-like recess portion is formed on the first area 1 of thetransparent base material in a position lying in proximity to an outercircumferential portion thereof, and the luminescent material layer 131is formed in the recess portion. This luminescent material layer 131 isa layer which contains a luminescent material which absorbs, when lightenters there from the primary light source 72, the light from theprimary light source 72 as excitation light to thereby be excited toemit light having a wavelength band of green which is one of the threeprimary color of light. By the luminescent material layer 131 beingformed in the way described above, the luminescent wheel 71 can functionas a light emitting plate. Note that this luminescent material layer 131is made up of a crystal of luminescent material and a binder.

A dichroic layer 132 is formed through coating on a surface of theportion on the first area 1 of the transparent base material on whichthe luminescent material layer 131 is to be formed, and this dichroiclayer 132 transmits excitation light and reflects light of otherwavelength bands. The luminescent material layer 131 is formed on thedichroic layer 132. Note that the dichroic layer 132 may be formed notonly at the portion where the luminescent material layer 131 is formedbut also over an overall surface of the first area 1. In addition, sincethe dichroic layer 132 only has to be provided between the primary lightsource 72 and the luminescent material layer 131, the dichroic layer 132may be formed on a side of the transparent base material which faces theprimary light source 72.

The second area 2, which is the transmissive portion, has the diffuselayer 141 on a side thereof which is an opposite side to a side whichfaces the primary light source 72. Specifically, this diffuse layer 141is formed as a layer which imparts a diffusing effect to light from theblue light source when the light is incident thereon by applying anoptical treatment such as a roughening treatment to the second area 2 ofthe transparent base material through blasting.

In addition to the case where the diffuse layer 141 is formed byapplying the optical treatment to the surface of the transparent basematerial, the diffuse layer 141 may be formed by securing a belt-likesolid material which is an optical material to the specific side of thesecond area 2. In addition, the diffuse layer 141 may be formed on theside of the second area 2 which faces the primary light source 72instead of the diffuse layer 141 being formed on the side of the secondarea 2 which lies opposite to the primary light source 72.

Further, a nonreflective coated layer, not shown, is formed over anoverall surface of the primary light source 72 side of the transparentbase material through coating.

In addition, in the luminescent wheel 71, the transparent base materialcan be formed of two filter pieces which correspond to the two segmentareas. Namely, a configuration can be adopted in which the luminescentmaterial layer 131 and the diffuse layer 141 are formed of the twofilter pieces, respectively and thereafter, the two filter pieces arecombined into a circular shape and are bonded together or are madeintegral with each other by means of an attaching member or the like.

In this way, the luminescent material layer 131 and the diffuse layer141 are disposed on the two segment areas so as to lie adjacent to eachother in a circumferential direction. Consequently, in the event thatlight from the blue light source is emitted sequentially on to theluminescent material layer 131 and the diffuse layer 141 on theluminescent wheel 71 which is rotating, when the light is emitted on tothe luminescent material layer 131 of the luminescent wheel 71,luminescent light having a green wavelength band is emitted from theluminescent wheel 71. When the light is emitted on to the diffuse layer141 of the transmissive portion of the luminescent wheel 71, the lightfrom the blue light source is passed through the luminescent wheel 71while being diffused.

Then, since the dichroic layer 132 is formed on the surface of the firstarea 1 of the transparent base material where the luminescent materiallayer 131 is disposed and the nonreflective coated layer is formed onthe primary light source 72 side of the transparent base material, whenlight from the primary light source 72 is emitted on to the first area1, the light from the blue light source passes through the nonreflectivecoated layer on the incident surface of the first area 1 so as to beincident on the transparent base material with almost no light beingreflected to the primary light source 72 side. Then, the light from theblue light source which has passed through the transparent base materialpasses through the dichroic layer 132 to enter the luminescent materiallayer 131.

A luminescent material on the luminescent material layer 131 absorbslight from the blue light source as excitation light and then emitsluminescent light having the green wavelength band in all directions. Inthe green luminescent light so emitted, the green luminescent lightemitted in an opposite direction to the primary light source 72 isincident on the light mixing unit 75 via the light guiding opticalsystem, which will be described later. The green luminescent lightemitted towards the transparent base material side is reflected by thedichroic layer 132, and much of the reflected light is incident on thelight mixing unit 75 via the light guiding optical system as lightemitted from the luminescent wheel 71.

Then, when laser light having a blue wavelength band enters the diffuselayer 141 from the primary light source 72, since the diffuse layer 141imparts the diffusing effect to the light of the blue light sourceincident thereon, blue light is emitted from the diffuse layer 141 whichis made into diffuse light similar to the emitted light (the greenluminescent light) from the luminescent material layer 131, and the bluelight enters the light mixing unit 75 via the light guiding opticalsystem.

In addition, as is shown in FIG. 5, the light source unit 63 includes acollimator lens 150. The collimator lens 150 is disposed on an existside of the primary light source 72 so as to convert light emitted fromthe primary light source 72 into parallel light. Additionally, the lightsource unit 63 includes the light guiding optical system which is madeup of a dichroic mirror 151 and a reflecting mirror 152, as well as alight guiding lens. The dichroic mirror 151 and the reflecting mirror152 are designed so that light emitted from the luminescent wheel 71which has a predetermined wavelength band is reflected thereon or passedtherethrough and optical axes of blue light and green light from theluminescent wheel 71 and an optical axis of red light from the secondarylight source 82 are changed in direction so as to be guided on the sameoptical path. The light guiding lens guides beams of light which areemitted from the luminescent wheel 71 so as to be incident on the lightmixing unit 75.

Hereinafter, the light guiding optical system of the embodiment will bedescribed.

The dichroic mirror 151 is disposed in a position where the optical axisof the primary light source 72 and the optical axis of the secondarylight source 82 intersect each other at right angles. The dichroicmirror 151 transmits blue light that is emitted from the primary lightsource 72 and which passes through the transmissive portion of theluminescent wheel 71 and green light emitted from the luminescent wheel71 and reflects red right emitted from the secondary light source 82 bychanging the direction thereof at an angle of 90 degrees.

The reflecting mirror 152 is disposed in a position where the opticalaxis of the primary light source 72 intersects the optical axis of thelight mixing unit 75 at right angles. The reflecting mirror 152 reflectsblue light and green light from the luminescent wheel 71 and red lightreflected by the dichroic mirror 151 by changing their directions at anangle of 90 degrees towards the light mixing unit 75.

By a light guiding lens group 155 being disposed in proximity to an exitplane of the luminescent wheel 71, beams of light emitted from theluminescent wheel 71 are guided so as to be shone on to the dichroicmirror 151.

Similarly, by a light guiding lens group 155 being disposed in proximityto an exit plane of the secondary light source 82, beams of lightemitted from the secondary light source 82 are guided so as to be shoneon to the dichroic mirror 151. Further, since a light mixing unitincident lens 154 is disposed between the dichroic mirror 151 and thereflecting mirror 152, respective beams of light of blue, green and redare incident on the light mixing unit 75 in the form of beams of lightwhich are concentrated further.

Consequently, when the luminescent wheel 71 is rotated and light isemitted from the primary light source 72 and the secondary light source82 at different timings, light having red, green and blue wavelengthbands is sequentially incident on the light mixing unit 75 from theluminescent wheel 71 via the light guiding optical system, and the DMD,which is the display device 51 of the projector 10, time-shares light ofred, green and blue in accordance with data for indication, whereby acolor image can be generated on the screen.

Then, the turning on and off operations of the primary light source 72and the secondary light source 82 are controlled to be time-shared bythe light source control means. The light source control circuit 41,which is the light source control means, controls so that light isemitted from the primary light source 72 so as to enter one of the firstarea 1 and the second area 2 and so that the emission of light isstopped so as to prevent light from the primary light source 72 fromentering a boundary position therebetween. Thus, by controlling theprimary and secondary light sources in that way, the light sourcecontrol circuit 41 controls so that the primary light source 72 isturned off and the secondary light source 82 is turned on so as toprevent the emission of light having a wavelength band which is acombination of wavelength bands of two colors from the luminescent wheel71.

Specifically speaking, a range where the primary light source 72 is tobe turned off is determined so that a substantially circularillumination area 7 illuminated by light from the primary light source72 is positioned so as not to stretch over the first area 1 and thesecond area 2. This primary light source turning-off range is a rangewhich is surrounded by tangents to an illumination area 7 illuminated bylight from the luminescent wheel 71 which lies in proximity to oneboundary of two boundaries between the first area 1 and the second area2 as is shown in the figure. These tangents are imaginary lines whichindicate a predetermined position on the luminescent wheel 71. Theprimary light source turning-off range is a fan-shaped area whose centerangle centered at a boundary line between the first area 1 and thesecond area 2 is referred to as an acute angle, and when this area ispositioned on an axis of the primary light source 72 which is disposedin a fixed position, the light source control means turns off theprimary light source 72.

Namely, the light source control means turns off the primary lightsource 72 when one of the tangents forming the fan-shaped area comes tobe positioned at the center of the illumination area 7 of the primarylight source 72 which is disposed in the fixed position by the tangentsmoving as a result of the rotation of the luminescent wheel 71, and thelight source control means turns on the primary light source 72 when theother tangent comes to be positioned at the center of the illuminationarea 7. In other words, the primary light source 72 is turned off whenthe boundary line moves to a position where it contacts the circularillumination area 7 as a result of rotation of the luminescent wheel 71,and the primary light source 72 is turned on when the boundary linepasses the illumination area 7 and moves to a position where it contactsanother illumination area 7.

Consequently, in order to prevent the mixing of colors in an ensuredfashion, the light source control means turns off the primary lightsource 72 when the boundary between the first area 1 and the second area2 of the luminescent wheel 71 which is rotating approaches theillumination area 7 of the primary light source 72 so that the primarylight source 71 is turned off in a wider range than the primary lightsource turning-off range. Then, the light source control means turns onthe primary light source 72 again when the boundary between the firstarea 1 and the second area 2 has passed through the illumination area 7of the primary light source 72. As a result, the mixing of colors can beprevented at one of the two boundaries between the first area 1 and thesecond area 2.

In addition, as is shown in FIG. 6( b), the range where the primarylight source 72 is to be turned off can be set to be wider than a sizeof the incident plane of the light mixing unit 75, whereby the mixing ofcolors of light from the luminescent wheel 71 which is incident on thelight mixing unit 75 in the range can be prevented in an ensuredfashion, thereby making it possible to obtain good color reproducingcharacteristics.

Note that the primary light source turning-off range depicted in thefigure may be configured as a range where the secondary light source 82is turned on and the primary light source 72 is turned off so as toprevent the occurrence of mixing of colors at the other of the twoboundaries between the two segment areas. However, the invention is notlimited thereto, and hence, a configuration may be adopted in which theprimary light source 72 is turned off and the secondary light source 82is turned on so as to prevent the occurrence of mixing of colors at boththe boundaries between the two segments, so that light of predeterminedwavelength bands is emitted from the light source 63 sequentially in theorder of red, green, red and blue, for example.

Next, timings at which the primary light source 72 and the secondarylight source 82 are turned on and off will be described by reference totime charts shown in FIG. 7.

In the figure, a wheel angle represents a position on the wheel surfaceof the luminescent wheel 71 shown in FIG. 6 (specifically, a position onthe wheel surface which is disposed at the center of the illuminationarea 7) in angle on the basis of understanding that one of the boundarylines between the first area 1 and the second area 2 is regarded as areference (0 degree). This position moves as the luminescent wheel 71rotates.

FIG. 7 (a) is a drawing showing a control under which light of red,green and blue wavelength bands is emitted from the light source unit 63at substantially equal intervals. Firstly, the light source controlmeans turns on the primary light source 72 when a wheel position at awheel angle of 60 degrees comes to be positioned at the center of theillumination area 7. Then, light emitted from the primary light source72 enters the luminescent material layer 131 which is formed on thefirst area of the luminescent wheel 71. Because of this, greenluminescent light (G) emitted from the luminescent wheel 71 is emittedfrom the light source unit 63 so as to be incident on the light mixingunit 75.

In addition, when the luminescent wheel 71 rotates further so that awheel position at a wheel angle of 180 degrees reaches the center of theillumination area 7, light from the primary light source 72 enters thediffuse layer 141 on the second area 2. Then, light from the blue lightsource (B) that has passed through the transmissive portion of theluminescent wheel 71 while being diffused is emitted from the lightsource unit 63 so as to be incident on the light mixing unit 75.

Then, when a wheel position at a wheel angle of 300 degrees, which is aposition lying just before the boundary between the first area 1 and thesecond area 2, comes to be positioned at the center of the illuminationarea 7 of the primary light source 72, the light source control meansturns off the primary light source 72 and turns on the secondary lightsource 82. Then, only light from the red light source (R), which isemitted from the secondary light source 82, is emitted from the lightsource unit 63 so as to be incident on the light mixing unit 75.

Further, when the wheel position at the wheel angle of 60 degrees comesto be positioned at the center of the illumination area 7 of the primarylight source 72, the light source control means turns on the primarylight source 72 and turns off the secondary light source 82. Then, greenluminescent light (G) is emitted from the light source unit 63.

Consequently, since light having the red (R) wavelength band, lighthaving the green (G) wavelength band and light having the blue (B)wavelength band are emitted sequentially from the light source unit 63,the projector 10 can generate a color image on the screen bytime-sharing the light of the respective colors which has been incidentin accordance with data at the display device 51 for display.

In addition, in order to prevent a reduction in luminance due to a statebeing produced in which neither the primary light source 72 nor thesecondary light source 82 is turned on, the light source control meanscontrols timings at which the primary light source 72 and the secondarylight source 82 are turned on and off so that either of the primarylight source 72 and the secondary light source 82 is turned on slightlybefore the other is turned off.

In addition, the secondary light source 82 which emits red light isinstalled as a single-color light source, and the primary light source72 and the secondary light source 82 are made to be controlledindividually by the light source control unit. Because of this,illumination times of the primary light source 72 and the secondarylight source 82 can be changed as required, whereby the light sourceunit 63 can be provided as light source unit which has a variety ofmodes of different degrees of brightness.

Additionally, light having wavelength bands of magenta (M) and yellow(Y) which constitute complementary colors can be emitted from the lightsource unit 63 by turning on both the primary light source 72 and thesecondary light source 82 simultaneously only for a predetermined lengthof time. Specifically speaking, as is shown in FIG. 7( b), when theprimary light source 72 is turned on so as to cause light from the bluelight source to enter the first area 1, green light (G) is emitted.Then, when the luminescent wheel 71 rotates whereby the light from theblue light source is caused to enter the second area 2, blue light (B)is emitted. Further, when the secondary light source 82 is turned onafter blue light has been kept emitted for a predetermined length oftime, blue light that has passed through the luminescent wheel 71 andred light emitted from the secondary light source 82 are combinedtogether so that light having a stable wavelength band of magenta (M)can be emitted from the light source 63 so as to be incident on thelight mixing unit 75.

Then, when only the primary light source 72 is turned off after themagenta light (M) has been kept emitted for a predetermined length oftime, the red light (R) from the secondary light source 82 is emittedfrom the light source unit 63. Further, when the primary light source 72is turned on without turning off the secondary light source 82 after redlight (R) has been kept emitted for a predetermined length of time, redlight from the secondary light source 82 and green light emitted fromthe luminescent wheel 71 are combined so that light having a stablewavelength band of yellow (Y) can be emitted from the light source 63 soas to be incident on the light mixing unit 75.

In this way, the light source control means not only controls to turn onthe primary light source 72 and the secondary light source 82individually separately but also controls to turn on the primary lightsource 72 and the secondary light source 82 simultaneously for thepredetermined length of time at the predetermined timing so that lightemitted from the luminescent wheel 71 when it receives light from theprimary light source 72 and light emitted from the secondary lightsource 82 are combined together for the predetermined length of time. Asa result, not only light of the primary colors but also light of thecomplementary colors can be emitted from the light source 63, wherebythe luminance of the light source unit 63 can be increased so as torealize an increase in color reproducing characteristics.

In addition, as is shown in FIG. 7( c), the light source control meanscan control the time during which the primary light source 72 and thesecondary light source 82 are turned on so that the emitting time oflight of each color is reduced, thereby making it possible to controlthe luminance of the light source unit 63 as required. Additionally, byadopting a configuration in which the light source control meanscontrols the primary light source 72 or the secondary light source 82 soas to suppress the output thereof only when light of a predeterminedwavelength band is emitted, tone can be controlled.

In addition, as is shown in FIGS. 4 and 6, the invention is not limitedto the configuration in which the luminescent wheel 71 is formed to havethe two segment areas but can adopt various configurations. For example,as is shown in FIG. 8( a), three segment areas are formed on atransparent base material. Then, a green luminescent material layer 131for emitting green light (G) is disposed on a first area 1. A diffuselayer 141 for transmitting blue light (B) is disposed on a second area 2to thereby form a transmissive portion. A mask 145 is disposed to covera third area 3 to thereby form a non-transmissive portion which preventsthe transmission of light from the primary light source 72.

In this way, by forming the non-transmissive portion which prevents thetransmission of light from the primary light source 72 on thepredetermined segment area and causing light of the secondary lightsource 82 to enter when light from the primary light source 72 is cutoff by the non-transmissive portion, red light (R) of the secondarylight source 82 can be emitted from the light source unit 63 while theprimary light source 72 is kept turned on.

In addition, as is shown in FIG. 8( b), a configuration can also beadopted in which three segment areas are formed on a transparent basematerial and a green luminescent material layer 131G is disposed on afirst area 1, a cyan luminescent material layer 131C is disposed on asecond area 2 which can emit light having a wavelength band of cyan,which is a complementary color, and a third area 3 is formed as adiffuse and transmissive portion.

In this way, the luminescent material layer 131 does not have to belimited to the luminescent material layer which emits luminescent lighthaving the green wavelength band. Thus, luminescent material layerswhich emit light of other various wavelength bands than the greenwavelength band may be provided as the luminescent material layer 131.In addition, as is shown in FIG. 8( b), a primary light sourceturning-on range is set to range from a wheel angle of 30 degrees to awheel angle of 330 degrees, and a secondary light source turning-onrange is set to range from a wheel angle of 270 degrees to a wheel angleof 90 degrees. Thus, by adopting this configuration, only light havingthe red wavelength band (R) from the secondary light source 82 can beemitted from the light source unit 63 when the center of theillumination range of the primary light source 72 is positioned withinthe range from the wheel angle of 330 degrees to the wheel angle of 30degrees.

Then, when the center of the illumination range is positioned in therange from the wheel angle of 30 degrees to the wheel angle of 90degrees, light having a wavelength band of yellow (Y) can be emittedfrom the light source unit 63 which is a combination of light having thegreen wavelength band which is emitted from the luminescent wheel 71 andlight having the red wavelength band which is emitted from the secondarylight source 82. Additionally, when the center of the illumination rangeis positioned in a range from the wheel angle of 90 degrees to a wheelangle of 150 degrees, only light having the green wavelength band (G)which is emitted from the luminescent wheel 71 can be emitted from thelight source unit 63.

Further, when the center of the illumination range is positioned in arange from the wheel angle of 150 degrees to a wheel angle of 210degrees, only light having the cyan wavelength band (C) which is emittedfrom the luminescent wheel 71 is emitted from the light source unit 63.In addition, when the center of the illumination range is positioned ina range from the wheel angle of 210 degrees to the wheel angle of 270degrees, only light having the blue wavelength band (B) which passesthrough the transmissive portion of the luminescent wheel 71 is emittedfrom the light source unit 63.

Then, when the center of the illumination range is positioned in a rangefrom the wheel angle of 270 degrees to the wheel angle of 330 degrees,light having a wavelength band of magenta (M) is emitted from the lightsource unit 63 which is a combination of light having the bluewavelength band which passes through the transmissive portion of theluminescent wheel 71 and light having the red wavelength band which isemitted from the secondary light source 82.

In this way, there can be provided the light source unit 63 which canemit light of various wavelength bands by disposing the different typesof luminescent material layers 131 or controlling the timings at whichthe primary light source 72 and the secondary light source 82 are turnedon by combining the timings variously.

Then, the types and locations of the light sources are not limited tothose of the embodiment described heretofore. Therefore, in place of thelaser emitter, a blue light emitting diode may be used as the primarylight source 72. A laser emitter which emits laser light of the redwavelength band may be adopted for the secondary light source 82. Inaddition, high-output excitation light can be emitted so as to excitethe luminescent material with good efficiency by adopting the blue laseremitter for the primary light source 72, and the production costs can besuppressed by adopting a red light emitting diode for the secondarylight source 82.

Further, the invention is not limited to the optical layout shown inFIG. 5 which is configured so that light emitted from the secondarylight source 82 is prevented from entering the luminescent wheel 71.Thus, an optical layout shown in FIG. 9 may be adopted in which asecondary light source 82 is disposed on the side where a primary lightsource 72 is disposed so that light from the secondary light source 82also enters a luminescent wheel 71. As this occurs, a dichroic mirror151 is installed in a position which lies between the luminescent wheel71 and the primary light source 72 and where an optical axis of theprimary light source 72 and an optical axis of the secondary lightsource 82 intersect each other at right angles. The dichroic mirror 151is designed to transmit light from the primary light source 72 and toreflect light from the secondary light source 82. Namely, light from thesecondary light source 82 can also enter the luminescent wheel 71.

In addition, as this configuration is adopted, as is shown in FIG. 10,the luminescent wheel 71 has a first area 1, a second area 2 and a thirdarea 3. Specifically, the first area 1 has a luminescent material layer131 which receives light from the primary light source 72 to emitluminescent light. The second area 2 functions as a transmissive portionwith a diffuse layer 141 which transmits light from the primary lightsource 72. The third area 3 functions as a transmissive portion whichtransmits light from the secondary light source 82. Then, by turning onthe primary light source 72 (while turning off the secondary lightsource 82) so that light enters the first area 1 and the second area 2and turning on the secondary light source 82 (while turning off theprimary light source 72) so that light enters the third area 3, light ofthe respective colors can be emitted sequentially from the light sourceunit 63.

In the event that the secondary light source 82 is made up of a laseremitter, by forming a diffuse layer 141 on the second area 2 and thethird area 3, highly directive laser light emitted from the primarylight source 72 and the secondary light source 82 can be passedtherethrough as diffuse light which is similar to luminescent lightemitted from the first area 1. Then, as this occurs, the diffuse layers141 disposed on the second area 2 and the third area 3 are formed inaccordance with characteristics of light caused to enter, and opticaltreatments of different specifications may be applied to the diffuselayers 141.

In addition, a configuration may be adopted in which in place ofdisposing the diffuse layers 141 on the transmissive portions of theluminescent wheel 71, the transmissive portions are formed of a normalglass plate or as space in the form of a through hole on the perimeterof which a frame is formed, and optical components which impart adiffuse effect are fixedly disposed on an optical path of laser light onthe primary light source 72 side in close proximity to the luminescentwheel 71 or on an exit side of the luminescent wheel 71. In addition, inthe event that the primary light source 72 and the secondary lightsource 82 are each made of a light emitting diode, the light source unit63 may adopt a configuration in which the diffuse layer 141 is providedon neither the transmissive portion nor the optical path.

In this way, according to the invention, due to the light source unit 63including the primary light source 72 which excites the luminescentmaterial, the luminescent wheel 71 having the type of luminescentmaterial with good light emitting efficiency and the secondary lightsource 82 which is the single-color light source for emitting light ofthe red wavelength band which corresponds to a luminescent material withrelatively low light emitting efficiency in place of forming, forexample, a red luminescent material on the luminescent wheel 71 as theluminescent material with relatively low light emitting efficiency,there can be provided the light source unit 63 which can increase theluminance of the screen of the projector 10 and the projector 10 whichincludes the light source unit 63.

In addition, since the configuration is adopted in which light from thelight source is caused to enter the luminescent wheel 71 at thepredetermined timing, compared with a case in which light is caused tostrike the luminescent wheel 71 at all times, the time during whichlight is shone on to the luminescent wheel 71 can be reduced so as tosuppress the increase in temperature. Consequently, a reduction in lightemitting efficiency can be suppressed which is attributed to an increasein temperature of the luminescent material, thereby making it possibleto increase the light emitting efficiency of the luminescent material.

Additionally, by adopting the laser emitter which emits light of theblue wavelength band for the primary light source 72, the luminescentmaterial can be excited with good efficiency for emission of light. Inaddition, by forming at least the luminescent material layer 131 havingthe luminescent material for emitting light of the green wavelength bandon the luminescent wheel 71, light having the wavelength band of greenwhich is one of the primary colors of light can be generated. Further,by providing the diffuse layer 141 on the transmissive portion, laserlight having directivity can be transmitted while being diffused so thatlight of the wavelength band of blue which is another of the threeprimary colors of light can be incident on the light mixing unit 75 asdiffuse light similar to luminescent light.

In addition, the invention is not limited to the embodiment and itsmodified examples. For example, in place of being provided on theprojector 10, the light source control means may be provided separatelyfor the light source unit 63. In addition, an optical layout may beadopted in which the dichroic mirror 151 shown in FIG. 5 is made into amirror having such characteristics that light from the luminescent wheel71 is reflected and light from the secondary light source 82 is passedtherethrough and the light mixing unit 75 is disposed on the opticalaxis of the secondary light source 82. Additionally, an optical layoutmay also be adopted in which the dichroic mirror 151 shown in FIG. 9 ismade into a mirror having such characteristics that light from theprimary light source 72 is reflected and light from the secondary lightsource 82 is passed therethrough and the positions of the primary lightsource 72 and the secondary light source 82 are replaced by each other.

In addition, in the embodiment, while the laser emitter which emitslight of the blue wavelength band is described as being used for theprimary light source 72, the invention is not limited thereto. Forexample, a laser emitter which emits light having a wavelength band ofultraviolet light may be used for the primary light source 72. As thisoccurs, a luminescent material layer is desirably disposed on thetransmissive portion of the luminescent wheel 71 which emits lighthaving a different wavelength band from light having a wavelength bandwhich is emitted by a luminescent material layer 131 which is formed ona reflective portion.

Additionally, in the embodiment, while the dichroic mirror is used forchanging the directions of the optical paths and selecting transmissionor reflection in accordance with wavelengths, the invention is notlimited thereto. For example, the dichroic mirror may be replaced byother alternative means such as a dichroic prism.

In this way, as is shown in FIGS. 5 and 9, since the light source unit63 can adopt the various optical layouts, not only can the luminance ofthe screen of the projector 10 be increased as has been described above,but also the degree of freedom can be increased in disposing the lightsource unit 63 in electric or electronic equipment such as the projector10 in which the light source unit 63 is installed.

Further, as to the segment areas formed on the transparent basematerial, the invention is not limited to the configuration in which thesegment areas are formed equal in size. Therefore, there may be aconfiguration in which four or more segment areas are formed althoughthose are not equal in size. In addition, a configuration may be adoptedin which a luminescent material layer 131 which emits light of the redwavelength band is disposed on the third area 3 shown in FIG. 10 andwhen the third area 3 is positioned at the center of the illuminationrange, both the primary light source 72 and the secondary light source82 are turned on so as to make use of the secondary light source 82 asan auxiliary light source for increasing the quantity of red light.Additionally, the secondary light source 82 is not limited in use to thelight source which emits light of the red wavelength band but may beused as a light source for emitting light of any wavelength band otherthan red wavelength band which differs from luminescent light emittedfrom the luminescent material layer 131 and excitation light emittedfrom the primary light source 72.

Further, there may be a case where the luminescent wheel 71 is formedinto a rectangular light emitting plate in place of being formed intothe disc shape and is disposed fixedly. As this occurs, by installing anadjusting unit for changing the emitting direction of light from theprimary light source 72 between the primary light source 72 and thelight emitting plate or providing a light source driving unit fordriving the primary light source 72 so as to change its position and orlight emitting direction, so that an illumination spot of light from theprimary light source 72 is positioned sequentially in the respectivesegment areas, light of the respective colors can be incident on thelight mixing unit 75 via the light guiding optical system. In addition,as the adjusting unit, for example, an optical deflector can be adoptedwhich utilizes a KTN crystal, an acousto-optic device, an MEMS mirror orthe like.

In addition, the invention is not limited to the embodiment and itsmodified examples and hence can be modified and improved as requiredwithout departing from the spirit and scope thereof.

While the invention has been described by reference to the varioustypical embodiments, the invention is not limited thereto. Consequently,the scope of the invention is only limited by claims appended hereto.

21 Input/Output Connector Part

22 Input/Output Interface

23 Image Transform Part

24 Display Encoder

25 Video RAM

26 Display Drive part

31 Image Compression/Expansion Part

32 Memory Card

35 Ir Reception Part

36 IR Processing Part

37 Keys/Indicators Part

39 Control Unit

41 Light Source Control Circuit

43 Cooling Fan Drive Control Circuit

48 Audio Processing Part

What is claimed is:
 1. A light source unit comprising: a light emittingplate which has a plurality of segment areas, wherein the light emittingplate includes a luminescent material which emits light having apredetermined wavelength band by receiving excitation light, and whereina rotation of the light emitting plate is controllable; a primary lightsource for emitting the excitation light onto the luminescent material;a secondary light source for emitting light having a wavelength bandwhich differs from wavelength bands of the luminescent light emittedfrom the luminescent material and the excitation light emitted from theprimary light source; a light guiding optical system for guiding lightemitted from the light emitting plate and light emitted from thesecondary light source to a same optical path; and a light sourcecontroller for controlling emission of light from the primary lightsource and the secondary light source; wherein: the light emitting platehas a fan-shaped area which defines a primary light source turning-offrange controlled by the light source controller, the fan-shaped areahaving an acute center angle centered at a boundary line between twosegment areas within the plurality of segment areas, and the fan-shapedarea being set to be wider than a size of an incident plane of a lightmixing unit to which light is guided via the light guiding opticalsystem; and the light source controller is configured to perform controlto turn off the primary light source when either one of lines whichdefine boundaries of the fan-shaped area comes to be positioned at acenter of a substantially circular illumination area of the light fromthe primary light source.
 2. The light source unit according to claim 1,wherein the light source controller is configured to perform control toturn off the primary light source and to perform control to turn on thesecondary light source so as to prevent the light from the primary lightsource from being emitted onto at least one boundary of the two segmentareas which are adjacent to each other.
 3. The light source unitaccording to claim 1, wherein the primary light source comprises a laseremitter which emits laser light having a wavelength band of blue.
 4. Thelight source unit according to claim 3, wherein the luminescent materialcomprises a luminescent material which emits at least light having awavelength band of green by receiving the excitation light.
 5. The lightsource unit according to claim 3, wherein the secondary light sourcecomprises a light emitting diode which emits light having a wavelengthband of red.
 6. The light source unit according to claim 1, furthercomprising: a dichroic mirror which is disposed in a position where anoptical axis of the primary light source and an optical axis of thesecondary light source intersect each other; wherein the dichroic mirroris adapted to transmit the light from the light emitting plate andreflect the light from the secondary light source or adapted to reflectthe light from the light emitting plate and transmit the light from thesecondary light source.
 7. The light source unit according to claim 6,wherein the light source controller is configured to perform control toturn on the primary light source and the secondary light sourceindividually separately, and to perform control to turn on the primarylight source and the secondary light source simultaneously so that thelight emitted from the light emitting plate by receiving the light fromthe primary light source and the light emitted from the secondary lightsource are combined together only for a predetermined length of time. 8.The light source unit according to claim 1, further comprising: adichroic mirror which is disposed in a position where an optical axis ofthe primary light source and an optical axis of the secondary lightsource intersect each other; wherein the dichroic mirror is adapted totransmit the light from the primary light source and reflect the lightfrom the secondary light source or adapted to reflect the light from theprimary light source and transmit the light from the secondary lightsource.
 9. A projector comprising: the light source unit according toclaim 1; a display device; a light source side optical system forguiding light from the light source unit to the display device; aprojection side optical system for projecting an image emitted from thedisplay device onto a screen; and a projector controller for controllingthe light source unit and the display device.
 10. The light source unitaccording to claim 1, wherein one of the plurality of segment areas ofthe light emitting plate comprises a transmissive portion.
 11. The lightsource unit according to claim 10, wherein the segment area comprisingthe transmissive portion is semicircular and comprises substantiallyhalf of an overall area of the light emitting plate.
 12. The lightsource unit according to claim 1, wherein a nonreflective coated layeris coated over an overall surface of a side of the light emitting platewhich is opposite to a side of the light emitting plate on which theluminescent material is provided.
 13. The light source unit according toclaim 1, wherein the light emitting plate includes a dichroic layer onwhich the luminescent material is provided, and wherein the dichroiclayer transmits the excitation light such that the excitation light isemitted onto the luminescent material and reflects at least theluminescent light emitted from the luminescent material.
 14. A controlmethod of a light source unit, wherein the light source unit comprises(i) a light emitting plate which has a plurality of segment areas, thelight emitting plate including a luminescent material which emits lighthaving a predetermined wavelength band by receiving excitation light,wherein a rotation of the light emitting plate is controllable, (ii) aprimary light source for emitting the excitation light onto theluminescent material, (iii) a secondary light source for emitting lighthaving a wavelength band which differs from wavelength bands of theluminescent light emitted from the luminescent material and theexcitation light emitted from the primary light source, and (iv) a lightguiding optical system for guiding light emitted from the light emittingplate and light emitted from the secondary light source to a sameoptical path, and wherein the control method comprises: turning off theprimary light source in a primary light source turning-off range definedby a fan-shaped area of the light emitting plate, the fan-shaped areahaving an acute center angle centered at a boundary line between twosegment areas within the plurality of segment areas, and the fan-shapedarea being set to be wider than a size of an incident plane of a lightmixing unit to which light is guided via the light guiding opticalsystem, wherein the primary light source is turned off when either oneof lines which define boundaries of the fan-shaped area comes to bepositioned at a center of a substantially circular illumination area ofthe light from the primary light source.
 15. The control methodaccording to claim 14, wherein one of the plurality of segment areas ofthe light emitting plate comprises a transmissive portion.
 16. Thecontrol method according to claim 15, wherein the segment areacomprising the transmissive portion is semicircular and comprisessubstantially half of an overall area of the light emitting plate. 17.The control method according to claim 14, wherein a nonreflective coatedlayer is coated over an overall surface of a side of the light emittingplate which is opposite to a side of the light emitting plate on whichthe luminescent material is provided.
 18. The control method accordingto claim 14, wherein the light emitting plate includes a dichroic layeron which the luminescent material is provided, and wherein the dichroiclayer transmits the excitation light such that the excitation light isemitted onto the luminescent material and reflects at least theluminescent light emitted from the luminescent material.